1. Field of Invention
This invention is directed to a powered too for abrading, grinding, polishing, or the like.
2. Description of the Related Art
The process of finishing surfaces typically requires numerous abrading steps consisting of a first step to roughly grind the surface to an approximation of the desired surface, an intermediate step of smoothing this surface to a near-finished quality, and a final step of polishing the surface to a high degree of smoothness. Typically, the abrasion is provided by a hard, gritty material, which is moved across the surface to be finished. Grindstones and sandpaper are common examples of hard gritty materials used as grinding media. These grinding media are mounted to the sanding head of a powered tool. The sanding heads are driven by a power source that moves the abrading material in a rectilinear motion, a simple spin motion, or a more complex random-orbit motion. Spin motion removes material fast but leaves a surface with swirl marks. Random-orbit motion is slow to remove material but leaves a surface free of swirl marks. An example of an electrically powered spin abrasion tool is U.S. Pat. No. 5,690,545 to Clowers et al. Although the transmission of the power to the sanding head is by means of a flexible shaft the movement of the sanding drive plate is both coaxial and on-axis with the drive shaft. Random-orbit tools differ from spin tools in that the movement of the sanding plate is eccentric, or off-axis, to the drive shaft.
There are known combination tools, which have means for optionally providing either spin or random-orbit motions. U.S. Pat. No. 4,744,177 to Braun et al. is an example of a combination tool. This patent discloses an abrading tool with two eccentricities about the armature shaft. It also has two compensating weights, which automatically position themselves about the eccentric head depending upon the direction in which the armature turns. Alternatively, U.S. Pat. No. 5,947,804 to Fukinuki et al. discloses a similar concept with a reversible motor and weights, which automatically adjust. Typically, these designs are for light duty sanders with a relatively small sanding plate of five or six inches. This size does not lend itself to efficient surfacing of large sheets of artificial stone. There exist standard radial arm polishers that are designed for marble and granite but they do not work well on artificial stone or other solid surface materials as the sanding action is solely from a spin motion and leaves swirl marks that are not acceptable to consumers.
The present invention relates to an abrasion tool that is capable of being configured for spin or random-orbit motion to finish solid surface materials without the need for an expensive reversible motor as required by the prior art. The tool uses two collars, each having half of the desired offset and half of the counterweight. In spin mode, the collars are rotated so that the counterweights and the offsets cancel each other and the head is balanced and concentric. The sanding plate is coupled to the collars for maximum sanding. This allows coarse sanding with minimal vibrations. In the random-orbit mode, the rotating collar is rotated 180xc2x0 so that the counterweights are aligned on one side of the axis of spin and the offsets are combined on the opposite side of the axis. The two collars are pinned to each other but not to the sanding plate. This allows the free rotation of the sanding plate on a shaft while the shaft is driven in an orbital motion. Means is provided for feeding water to the sanding head to assist in finishing those materials that benefit from wet grinding.